Our love affair with chocolate is much older than we thought, and newly discovered traces of cocoa on ancient pots suggest it started in the rainforests of what is now Ecuador some 5300 years ago.
That's nearly 1500 years older than earlier evidence, and it shifts the nexus of cocoa production from Central America to the upper Amazon.
"This is an incredibly strong demonstration," says Rosemary Joyce, an archaeologist at the University of California, Berkeley, who was not involved in the new study. "It puts to rest any lingering claims that the use of [cocoa] pods … was an invention of the people of Mesoamerica."
The ancient civilizations of Central America, including the Olmec and Maya, processed cocoa seeds to produce drinks for use in rituals and feasts as far back as 1900 B.C.E., according to ancient texts and ethnohistoric accounts. Some researchers thought these civilizations were the first to take cocoa pods from the Theobroma cacao tree, drying, fermenting, roasting, and grinding them into a paste used to make the beverages.
But Joyce and other researchers wondered whether cocoa had an earlier, lost history. Genetic studies hinted as much, confirming that the cocoa tree is at its most genetically diverse in the humid forests of the upper Amazon. This suggests the upper Amazon is where all wild cocoa trees originally grew, and where humans would have had the original opportunity to exploit and cultivate it.
That was on the mind of Michael Blake, an archaeologist at the University of British Columbia in Vancouver, Canada, as he worked with colleagues—including archaeologist Francisco Valdez of the French Research Institute for Development in Marseille—at Santa Ana-La Florida in Ecuador. This ancient village is the oldest known site of the Mayo-Chinchipe culture, which occupied the western Amazon around 5500 years ago.
"I noticed they had found some very elaborate pottery, and I suggested that the vessels kind of reminded me of the ones that the Maya used to make cacao [drinks]," Blake says. "I asked: ‘Is there any chance that these vessels might also have been used for cacao?' And the answer came back: ‘Well, nobody's looked.'"
Blake and his colleagues have now used three independent lines of evidence to argue that the ancient vessels—which include unadorned bowls and elaborately decorated spouted bottles—once held cocoa. They scraped charred cooking residue from the inside of pot sherds for analysis and found they contained starch grains with a shape only seen in cocoa tree seed pods. They also had the chemical signature of theobromine, a compound present only in mature cocoa seeds. The final clincher came from an analysis of ancient DNA extracted from the pottery, which matched sequences from modern cocoa trees.
Rainforests pump water round the tropics—but the pulse of this heart is weakening
Collectively, the evidence suggests the inhabitants of Santa Ana-La Florida used cocoa routinely between about 5300 and 2100 years ago, according to pottery from carbon dated layers at the site. That makes the new find the oldest recorded use of cocoa, the team reports today in Nature Ecology & Evolution.
Previously, some of the oldest evidence came from 3100-year-old pottery vessels from Honduras, discovered by Joyce and colleagues. Joyce says the fact that Honduras is so far south—and that wild cocoa trees seem to be native to South America—led her to suspect that even earlier evidence of cocoa use would be found farther south. "These findings come as a welcome confirmation."
But Joyce questions whether the ancient inhabitants of Ecuador actually domesticated cocoa. She points out that they could simply have collected pods from the wild cocoa trees growing there.
Genomic evidence hints at domestication farther north, says Juan Carlos Motamayor Arias, an agricultural engineer at Universal Genetic Solutions LLC in Miami, Florida. Earlier this month, Motamayor Arias and his colleagues published a genomic analysis that traced the genetic fingerprint of cocoa domestication to about 3600 years ago in Central America. He says his research team found no genetic signal of domestication in samples from the upper Amazon region, where Santa Ana-La Florida lies.
Blake and his colleagues counter that the people of Santa Ana-La Florida likely domesticated the plant, given that they found cocoa residue on 19 different artifacts used over the course of thousands of years. The researchers also say domesticating a long-lived tree species might not have left a clear genetic signal until the trees were exported to Central America, where there are no wild cocoa trees to interbreed with domesticated forms.
Exactly how cocoa trees made that journey thousands of kilometers north is, for now, perhaps the biggest mystery. Cocoa seeds quickly lose viability during storage, so they are not easily transported. Some artifacts at Santa Ana-La Florida suggest the site had connections to the Pacific Ocean. "Could people have taken boatloads of seedlings and moved them up the coast?" Blake wonders.
He also thinks the new discoveries hint that the ancient cultures of South America had far more influence on the development of the later grand civilizations of Central America than researchers have thought, particularly given that the vessels at Santa Ana-La Florida are of a similar style to those used later in Central America. "That's definitely something we want to look at and research further."
